Genetic parameters and indirect selection of elite lines for efficiency in symbiotic nitrogen fixation in black common bean

This study aimed to evaluate whether managing populations and progenies of black common bean (Phaseolus vulgaris L.) in exclusive symbiotic nitrogen fixation (SNF) systems, which refer to environments where the primary nitrogen source in the soil is the SNF, is efficient for selecting lines with high symbiotic performance, using grain yield as a selection criterion, and to verify the relationship between agronomic- and SNF-related traits. A total of 76 black common bean lines from a single population and five checks were evaluated during the winter seasons of 2021 and 2022 under SNF systems. The experimental design was a 9 × 9 triple lattice. Evaluated traits included yield, 100-seed weight, and grain appearance. The top 10 and bottom 10 lines were selected based on grain yield in the field and evaluated with rhizobia inoculation in two greenhouse trials with five checks, using a randomized block design with four replications. Traits assessed included chlorophyll content, shoot and root dry weight, nodule number, nodule dry weight, and specific nodule weight. Genetic variability among the lines allowed for the selection of genotypes with high symbiotic performance. Significant differences were found between the groups of top and bottom lines for specific nodule weight, indicating its potential as a selection indicator. Significant correlations were found among the traits. Specific nodule weight, chlorophyll content, and shoot dry weight were identified as key factors for the indirect selection of genotypes with better symbiotic performance. Eight lines were selected for advanced trials to develop black common bean cultivars for SNF.